Free residual chlorine

The sum of hypochlorous acid (HClO) and hypochlorite ion (OCl^–) present in water is called residual free chlorine with the chemical symbol Cl₂ and can kill microbes. Care must be taken in sampling and sample storage because chlorine is not stable in aqueous solution. The chlorine content of samples or solutions, especially weak solutions, decreases rapidly. Exposure to sunlight or other strong light or stimulation accelerates the reduction of chlorine. Therefore, we begin measuring chlorine immediately after sampling, avoiding excessive light and agitation. We should not store samples that we analyze for chlorine.

Advantages of chlorination

We use chlorination of water sources and contaminated waters to destroy or inactivate disease-causing microorganisms, disinfect drinking water, and keep swimming pools clean and sanitary. We also use it in drinking water treatment to improve the overall quality of water by reacting chlorine with ammonia, iron, manganese, sulfide, and some organic materials. As a result, its presence is an indication of the effectiveness of the disinfection system and the ability of the water to combat microbial contamination.

Disadvantages of chlorination

Chlorination can cause adverse effects. The taste and odor characteristics of phenols and other organic compounds in the water source may be enhanced. Carcinogenic chlorinated organic compounds, such as chloroform, may be formed. Combined chlorine from chlorination of ammonia or amine-containing waters has adverse effects on some aquatic life. To achieve the primary purpose of chlorination and minimize any adverse effects, it is essential to use appropriate testing methods.

Chlorine measurement method

1- We determine the amount of free chlorine using accurate kits.

2- We determine the amount of chlorine using the titration method and laboratory reagents and equipment.

3- With electronic devices: These devices use electrochemical sensors to digitally display the concentration of free chlorine in milligrams per liter.